Typically, a floating ball type static flowmeter, such as that used to measure the flow rate of a gas passing through fluid conduits or tubing from a gas supply source to a gas user device, includes in the fluid path a transparent, vertically positioned tube through which the gas from the source is passed before transmission to the users device. A ball, usually spherical in shape, is positioned in the tube to rise and fall depending on the pressure applied to the ball as determined by the flow rate of the gas passing through the tube. A visual scale may be etched or printed along the barrel of the tube or a transparent housing enclosing the tube, the scale indicating the flow rate of the gas, e.g., in liters per minute (lpm), by the position of the ball against the scale.
Although simple in concept, the construction and assembly of such flowmeters can be complex and/or expensive if accuracy in flow rate measurement is needed. To provide relative accuracy, the flowmeters often are individually tested after assembly and the measuring scale added to the barrel of the tube or housing corresponding to the position of the ball after a test gas is passed though the tube at known flow rates from a minimum flow rate, e.g., 1 lpm, to a maximum flow rate, e.g., 15 lpm. Moreover, as uses of specific gases, such as oxygen or a concentrated oxygen mixture, in medical applications become more commonplace to permit patient mobility, factors such as cost, weight and simplification of design and assembly become more important considerations. For these and other purposes, we have developed an improved flowmeter that retains the simplicity of a ball-type flowmeter, but is more efficient and less costly to assemble. Because the flowmeter design according to our invention is very flexible, it also is possible to produce flowmeters of different capacities with a minimum of changes in parts.